Multi-set segmented windings are commonly used in modern electrical machine applications, such as in hybrid-electric vehicles. These windings typically comprise a plurality of U-shaped segmented conductors which include two legs and a central U-turn portion between the legs. The U-shaped conductors are often formed with a rectangular cross-section. The U-shaped conductors are positioned in the slots of a core portion of the electric machine, such as the stator slots, to form armature windings for the machine. These U-shaped conductors may also be referred to herein as “U-shaped bars”. The terms “U-shaped conductor”, “U-shaped bar” and “U-turn portion” are not intended to refer to a conductor or a conductor portion that forms a perfect “U” shape, but instead refers to a conductor or a conductor portion where the conductor changes axial direction by more than 90°, such as by about 180°. The term “hairpin” as used herein is not intended to be limited to U-shaped conductors, and instead refers generally to a distinct conductor segment having two ends, whether or not a U-shaped portion is included between the two ends.
With multi-set segmented hairpin windings, the U-shaped conductors are created by bending and twisting wire bars into U-shaped conductors with two legs and a U-turn between the legs. The two legs are separated by a given span which allows the conductor to extend across a number of stator slots by virtue of the U-turn alone. The legs of the hairpin conductors are then inserted into the slots from an insertion end of the stator. Following insertion of the hairpins, the bend portions are provided on one side of the stator (the “insertion side”) and the leg ends extend from the other side of the stator (the “connection side” or “weld side”). The legs ends are then bent to appropriate positions, with a first leg typically bent in one direction and another leg bent in the opposite direction such that the entire hairpin extends a given slot span (e.g., 12 slots). Finally, the proper leg ends are connected together at the connection side of the stator to complete the windings. These connections include adjacent leg ends that are aligned directly and welded together, non-adjacent leg ends that are connected through jumper wires, and terminal connections that lead to the winding phases. Together, the connected conductors form the complete armature winding arrangement.
With the above winding arrangement, the insertion side of the stator is typically clean and includes only the U-shaped turn portions of the conductors. However, the connection side is significantly more crowded. First, the leg ends, which are already very closely aligned at the connection side, are made even more crowded by the welding points between adjacent leg ends. In addition, the connection wires, including jumpers between windings sets, phase path connections, neutral connections, and terminal connections cause additional jam in the crowded hairpin welding points. The resulting clearance reduction between conductors creates potential short circuits during welding and other defects during production.
In addition to crowding at the connection end of the stator, the additional jumpers and terminals require more clearance for the electric machine at the connection end. In many applications, including hybrid electric vehicle applications, the compartment holding the electric machine is already crowded and it is difficult to find additional space for the increased clearance of the electric machine at the connection end.
Accordingly, it would be advantageous if a winding arrangement could be provided where the overall clearance required for the electric machine in an application compartment is decreased. It would also be desirable to provide a multi-set segmented hairpin winding arrangement where the crowding at the connection end of the stator is reduced. It would be of further advantage if such winding arrangement could be provided such that the electric machine may be easily manufactured, thus reducing manufacturing costs. It would also be advantageous if the winding arrangement resulted in decreased incidence of manufacturing errors.
It would be desirable to provide an electric that provides one or more of these or other advantageous features as may be apparent to those reviewing this disclosure. However, the teachings disclosed herein extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the above-mentioned advantages.